Any PEX tubing layout suggestions.........

PG

I'm installing tubing in a addition on my own home. I am a heating contractor but we do very little radiant (mostly just some repair work since our work area is existing homes.....lot's of steam, hot water baseboard, etc). I'm putting PEX in a lightweight concrete pour. I have done the heatload but it's the little things I'm not 100% sure of. Such as how tight to space the tubing in front of the doorwalls? Any pointers on the finer points would be greatly appreciated.

hr

Most times

the design software will tell you the needed tube spacing. If you do a heatload and design on any of the Radiant software this will show up.

Generally 12" on center will get most loads. Large glass areas may benefit from tighter spacing. Again the software will show areas where, and how close, "banding" is needed.

I like to tube bathrooms on a tighter 8" spacing for more consistent temperatures and quicker response, if zoned seperatly.

hot rod

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mp1969

Spacing

I like to put tubing at about 8" centers also in front of sliding doors and exposed walls to create a little thermal barrier where it is needed most. Wirsbo and our heating designer do this as routine now as radiant systems evolve.Make sure you test and keep the test on during the pour (this surfaces any punture holes or other leaks before they are literally set in stone).
I am sure that Hot Rod has a lot more experience as he does alot of these, but we try to keep the loops the same length to make balancing very easy and without expensive flow control valves etc. We also reverse return in order to create balanced flow in loops.

Good Luck!

Mp 1969

Steve Garson_2

If you plan on any carpeting, throw rugs, or big stuffed furniture, make sure that you account for it in planning, since they all reduce the radiation of heat.

Weezbo

a thought or two,

do your best to stay a "hand" off perimeter walls and around interior partitions,the carpet layers like to poke holes in the stuff...put plenty under bath areas yet stay away from the flanges, bringing the pipes out where someone might put thier feet in the mornings, same goes with cabinets and vanities, also block out tub and shower drains with a removeable cover, bring loops to one common area in a partition or wall to make a station that you can purge and bleed air from the system...with a by pass ahead of the valved headder so you can verify boiler water at station should the slab go down for any length of time... if you need 272 feet per loop Put it in the slab dont bust out the scissors and start whacking the loops into a variety of different lengths for the ease of installation...should you Nail the tube cut some holes in the floor cut the tube at the inadvertent nail hole stuff both ends about a foot back from one another down under the floor, couple ,insulate, tape over the floor where the holes are and carry on.. pressure testing is a good idea and leaving plenty of slack as it rounds corners and heads up into headders spaces is also good idea...wrapping the "tails" or headder With tinfoil and identifying supply and return" Then "is a good idea vs say after they have been thouroughly mud taped textured primed and painted ... good luck theres lots of easy things to help ..here is one more ,place the headder when you are near 50 60 feet or so to the end of the tubing. it makes "Getting it in there" part work out a little better. *~/:)

Constantin

I'd consider Dans primer...

... as a start. Hydronic Radiant Heating is a great starting point with lots of useful information. I'd also inform myself about pri-sec, if you don't know it already because most boilers in the US still don't like the cold return temperatures that radiant systems develop.

In my own home, we gave ourselves 6" off the finished wall (to avoid carpet nails), then put in the first set of loops on 6" centers, followed by 12" centers for the rest of the room. The slab is 4" thick, and optimal tube spacing depends on the thickness of the pour. The hottest water was designed to flow to the perimeter of the home first. We used ½" O₂-barrier PEX with loop lengths about 270' long. One manifold covers the entire basement.

Making the loops tighter in front of large glass surfaces is a great way to help ameliorate/combat dropping cold air convection currents at night, so going tigher in those locations makes a lot of sense. I have also seen homes where small, in-floor radiators or external raditators were placed under the windows for the same purpose. Most residential construction doesn't need that though.

Most importantly, and not related directly to the excellent emitter choice you're making, is the thermal envelope of the house. I highly recommend the builder series of books that the Building Science Corporation publishes. They're full of good building tips to keep the place as energy efficient as possible, such as using deeper studs (6") on 24" centers, etc. I'd also spend some time researching your insulation options. A great choice is dense-pack cellulose though foam may give you a performance advantage (that is $$$ and perhaps unjustifiable). Also, look into unvented roof systems which may reduce your energy needs further. Cheers!

PG

Ameliorate?????? I'm running for my dictionary...........

But thanks for the tips. I have seen the in floor radiators (fin tube). They seem like a great idea, (other then the crap that will undoubtly fall into them). I am a bit concerned about all the glass. I have two door walls, one is 8'. Plus a bunch of double-hungs spaced pretty close to each other. But I did do a heat load, and all in floor should do fine. Just tossing around the spacing issue.

PG

Good ideas........but do I put manual vents in the second floor?

Also any tricks when feeding to the second floor? Ever run into problems with tight bend radius'?

singh

Webster's Dictionary

Verb.

Make something bad , better. Ameliorate.

PG

I'm impressed!

You guys sure are smart. Not only am I going to have the baddest in-floor heat in town, but I'm going to be a smartty pants too! Thanks guys. Sharp as a bowling ball here in MI.

Unknown

If this is a thin pour (1.5" or so), do not allow the tubing to be greater than 9" o.c. under tile or wood, or you may get heat striping during shoulder seasons especially. This will be even worse if you're in a mild climate.